Odd One Out

[trenhoj]

Swadloon evolves.

Pikachu, Onix, Voltorb

 

[magicarp4thewin]

Pikachu, only Pokemon who evolves with a stone

Whimsicott,chesnaught,swadloon

 

[Squirrel]

Whimsicott, it's the only one to have evolved with a stone!

Tauros, Miltank, Bouffalant?

 

[Lycanthropy]

Bouffalant is the only one which has both genders.

Mew, Ditto, Zoroark

Flareon, Swadloon, Pachirisu

I see what you did there. ;)

 

[Squirrel]

I see what you did there. ;)

Oh hey I just got it, that's so cool XD

Mew is the only one that can't have Impostor as a hidden ability, but Zoroark is the only one that can't learn Transform, SO Ditto is the odd one out due to being the common theme in both of those cases. :D

Umbreon, Vaporeon, Glaceon?

 

[DyingWillFlareon]

Umbreon doesn't learn Ice Type moves via level up!

Shaymin, Regigigas, Darkrai

I see what you did there. ;)

Oh hey I just got it, that's so cool XD

Heheheheh you caught me.

 

[Lycanthropy]

Darkrai is the only one whose base speed isn't 100.

Medicham, Emboar, Hawlucha

 

[Squirrel]

Hawlucha is the only one who can turn moves into a different type!

Snorunt, Spheal, Avalugg?

 

[Voliol]

Spheal, it's the only one without separated hind legs.

What about Magcargo, Pinsir and Sandslash?

 

[Squirrel]

Magcargo, it's the only one that can't walk!

Uxie, Cobalion, Phione?

 

[Meadow]

Cobalion is the only one that doesn't float! (Plus, it's the only one from Generation V.)

Bulbasaur, Turtwig, Oddish

 

[Lycanthropy]

Turtwig is no poison type.

Kecleon, Zangoose, Miltank

 

[Squirrel]

Kecleon is the only one that can change types!

Ledyba, Wooper, Horsea!

 

[Olli]

Horsea, because that was picked over my suggestion. Also it's the only Pokemon that has 3 evolutionary stages

Cubchoo, Teddiursa and Mothim

 

[Venitardus]

Mothim because it flys and it isn't in its base form nor a bear.

Heatran
phione
Articuno

 

[Squirrel]

Articuno is the only one that's part of a trio so she's the odd one out!

Ariados, Minccino, Gothitelle?

 

[Virtual Headache]

Gothitelle is the only one which doesn't look like an animal. It also has no visible feet unlike the others.

Togepi, Pichu and Munchlax?

 

[Lycanthropy]

Munchlax is the only one not introduced in Gen II.

Blissey, Leavanny, Crobat

 

[Squirrel]

Blissey is the only one with a baby form!

Stantler, Tauros, Bouffalant?

 

[BumpsnStumps]

Vaporeon. It isn't dual-typed.

Lucario, Scizor, Braviary